Incidental mortality of seabirds associated with longline fishing in Subarea 48.3 – preliminary results of scientific observations onboard the Chilean longliner, Puerto Ballena, from March to May 1996

Estimates of the number of seabirds taken incidentally in longline fisheries on Patagonian toothfish (Dissostichus eleginoides) are still based on limited information. We report here on observations on the by-catch of seabirds during a cruise of the Chilean longliner 'Puerto Ballena' in Statistical Subarea 48.3. A total of 118 dead black-browed albatrosses, 3 dead grey-headed albatrosses, 46 dead white-chinned petrels were reported by the observer and crew members. In addition 21 black-browed albatrosses, 4 giant petrels, 1 white-chinned petrel and 1 unidentified penguin became hooked alive and were released alive. Our preliminary analysis confirmed results from last year that black-browed albatrosses are particularly at risk when longlines are set during the day and/or the streamer line is malfunctioning. If setting of lines had been restricted to nighttime as required in order to comply with Conservation Measure 29/XIV(CCAMLR, 1995) the number of black-browed albatrosses and white-chinned petrels taken incidentally would have been substantially lower. The by-catch of both black-browed albatrosses and white-chinned petrels appeared to decline towards the end of April/begriming of May. The estimated total catch for all observed sets was 312 black-browed albatrosses and 213 white-chinned petrels. This estimate should be regarded as tentative as there rue still problems associated with extrapolating observed numbers of dead seabirds from a subsample of hooks to the total number of hooks in a set which warrant further investigation. However, even if we consider the number of dead birds recorded by the observer and by crew members as a minimum estimate, these figures appear by far too high to be sustainable by both black-browed albatrosses and white-chinned petrel populations in the area.